The present invention relates to a mixing capsule and to a mixer unit which includes a mixing capsule, in particular for the production of a dental material which preferably contains a plurality of components.
Mixing capsules which are filled with the components in separate chambers by the manufacturer are used to produce mixtures of two or more components. The components are brought into communication and mixed with one another by the user, for example by destroying a wall separating the chamber.
Mixing capsules for the production of dental materials which are often mixed from a pulverulent component and a liquid component, the mixing procedure usually taking place in a shaker unit, are known in the dental sector. The fully mixed substance is then dispensed directly onto the working area, for example into a tooth cavity, through a dispensing spout formed integrally on the mixing capsule.
DE 36 35 574 A discloses a mixing capsule intended for the production of jointing and sealing compounds. In an illustrative embodiment described in said document, an auxiliary chamber which is present in the dispensing piston is delimited, on the side facing the main chamber of the capsule, by a foil and, on the opposite side, by an auxiliary piston which is arranged displaceably in the dispensing piston. In the initial state of the mixing capsule, in addition to the second component, a mixer body is accommodated in the auxiliary chamber, which mixer body initially serves to destroy the foil by means of manual displacement of the auxiliary piston and then assists in the mixing procedure. To allow the reduction in volume which is necessary for displacement of the inner piston together with ball, a gas cushion is provided in the mixing chamber.
In a further embodiment of the known mixing capsule, the mixing ball is initially situated in the main chamber. In this case, the auxiliary chamber present in the piston is closed off from the main chamber by means of a cover and on its rear side by a bellows. As a result of manual pressure being applied to the bellows, the cover is pressed away from the piston, so that the two chambers are brought into communication for the purpose of activating the capsule.
In both cases, a dedicated working step which has to be carried out manually is required for activation of the capsule. Furthermore, a gas cushion is required in order to permit the reduction in volume which is required for removal of the cover.
In a multicomponent mixing capsule for dental purposes which is known from DE 94 00 374 U1, a first component is contained in a mixing chamber and a second, liquid component is contained in a foil bag which is arranged in an auxiliary chamber which is separated from the mixing chamber by a displaceable wall element. A cylindrical mixing body which is present in the mixing chamber is used to displace the wall element at the start of the mixing procedure and thus to compress the foil bag, so that the latter bursts open and releases the liquid component through a liquid passage which is present in the wall element.
One difficulty with this device lies in designing the wall element, the film bag and the capsule itself in such a way, and in dimensioning these components with sufficiently low tolerances, for the wall element to be held in its starting position while the capsule is being stored and transported but to be displaced sufficiently far and with such force, under the action of the mixing body, that the foil bag bursts open. In this context, it should be borne in mind that the fact that the foil bag is often only partially emptied leads to undesirable changes in the mixing ratio and therefore to deterioration in the properties of the finished mixture. Another drawback is that this arrangement is suitable only for mixing, but not for application of the paste.
DE 93 03 268 U1 describes a multicomponent mixing capsule with ejection device for a mixed compound, primarily for dental purposes. This mixing capsule has an activation mandrel which is located in the interior of the capsule and is anchored against the direction of ejection by means of holders in the interior of the capsule body, and a liquid compartment which is accommodated in the interior of a ram and is sealed off with respect to the activation mandrel by a destructible membrane. The activation mandrel fits flush into the empty vessel in the interior of the ram and seals the latter while the material is being forced out.
While the material is being forced out in the longitudinal direction, the liquid passes through the thin capillary, which comes to lie in the interior of the activation mandrel, into the mixing space. It is explained that, even during the mixing operation in a vibration mixer and during the dispensing of the compound via the ejection nozzle, a small residue of liquid, which is not precisely reproducible, always remains in the capillary. This impairs the quality of the results of mixing.
A comparable mixing capsule is described in WO 00/30953.
The object of the present invention can primarily be regarded as that of making available an improved mixing capsule which avoids the abovementioned problems without impairing the desired results of mixing.
A further object can be regarded as that of making available a method for mixing and dispensing mixtures from mixing capsules, which method requires a smaller number of steps.
This object is achieved by a mixing capsule and a method for producing a mixing capsule as described in the claims.
The words xe2x80x9ccomprisexe2x80x9d or xe2x80x9cincludexe2x80x9d within the meaning of the invention precede a nonexhaustive list of features. The word xe2x80x9conexe2x80x9d is to be interpreted as an indefinite quantity with the meaning of xe2x80x9cat least onexe2x80x9d.
The mixing capsule according to the invention has, inter alia, the following advantages:
The movable body which is present in the mixing capsule serves not only to activate the capsule by destroying the separating device and to assist in the mixing procedure, but also serves as a displacement body during emptying.
The mixing capsule according to the invention also permits reproducible mixing of highly viscous substances.
Since, in the initial state, the body is situated in the main chamber, the activation preferably takes place automatically at the start of the mixing procedure, in contrast to the activation steps, known from the prior art, which have to be carried out manually.
Since, furthermore, the auxiliary chamber is separated from the main chamber by the separating device through which the body can penetrate, during the subsequent mixing procedure it forms part of the mixing chamber itself. This ensures that the second component included in the auxiliary chamber completely enters the mixture which is being formed.
Moreover, the unification of main chamber and auxiliary chamber advantageously increases the available mixing volume.
In the final phase of the dispensing procedure, the body assists in the virtually complete emptying of the mixing capsule interior formed by the main chamber and auxiliary chamber.
A further advantage is the small number and simple design of the components of the mixing capsule.
An advantage over the mixing capsule known for example from DE 23 24 296 A is that, because there is no need to arrange a foil cushion on the outside of the cartridge, together with a clasp for holding it, the capsule can have a smaller radial diameter with the same volume. This makes it easier to apply the mixture or compound from the capsule into a cavity of a tooth.
As appropriate, a plurality of freely movable bodies are located in the mixing capsule.
The movable body is preferably of spherical configuration. The diameter of the sphere is preferably in the range of 4 to 10 mm, particularly preferably in the range of 5 to 8 mm.
However, any other configuration of the body is also conceivable, for example an egg-shaped or lens-shaped configuration, or a configuration in the form of a platonic body. Depending on the chosen separating layer, such a configuration can more easily destroy the separating layer and, as appropriate, permits a smaller mass and/or size of the body.
The configuration of a body with corners and edges can also be favorable for dispensing the mixture from the capsule. Such a body cannot fit uniformly into the auxiliary chamber. There are therefore different width distances between the surface of the body and the inner surface of the auxiliary chamber. These facilitate the flow of the mixture when dispensing in the direction of the dispensing spout.
It can also be advantageous for the body to be designed in a ring shape. Depending on the size of the ring, the latter can engage to a greater or lesser extent into the auxiliary chamber and act there as a displacement body.
In a further embodiment, the piston is configured in such a way that it can deform, in particular plastically deform, during dispensing.
This can be achieved by the fact that the piston, which has at least one auxiliary chamber, consists of a deformable material or comprises such a material.
Another expedient configuration is one which has a geometric shape which facilitates the deformation.
A configuration of the piston which has proven expedient is one in the form of a hollow piston open at both ends with a first indent and a second indent, the first indent forming, together with the separating device, the auxiliary chamber.
Such a form can be obtained, for example, by pushing in the bottom surface of a beaker made of a deformable material. The pressing-in is preferably done using a ram.
It is also conceivable for such a piston to be produced by injection-molding or thermoforming of a deformable material.
For better sealing of the piston against the capsule wall, the piston preferably has one or more sealing lips.
An additional sealing action can be obtained by a configuration which, during the application procedure, allows the collapsible piston to spread open and press against the capsule wall.
Among others, the combination of a lens-shaped body in conjunction with a deformable piston has proven expedient.
To ensure more complete dispensing of the mixture from the mixing capsule, it can also be advantageous to arrange a projection on the outside of the piston base. Such a projection can be in the form of a thickened part of the piston base or in the form of a spacer piece, which is preferably cylindrical.
Since an application device having a displaceable piston rod and a ram with a defined and commercially standardized length is needed for dispensing the mixture, it is in some cases necessary to lengthen the axial length of the ram beyond the projection. In this way it is possible to ensure that the deformable piston can be displaced into the area of the dispensing spout. Another advantage is that there is less risk of the piston rod or the ram of the application device being jammed upon deformation of the piston of the mixing capsule.
The weight of the movable body is adapted to the nature of the separating device in such a manner that, during normal transport and normal handling, the separating device is not damaged by the movable body. The separating device can only be penetrated once acceleration values of, for example, 100-500 g (1 g=9.81 msxe2x88x922), preferably 200-400 g, which customarily occur in capsule mixer units, are reached.
Materials which are usable for the ball or body have a density in the range of 2 to 12 g/cm3. The mass of the ball usually lies in the range of 0.1 to 10 g, preferably in the range of 0.3 to 3.0 g.
The shape of the auxiliary chamber is preferably essentially a hemisphere with a radius which is slightly larger than that of the body. This is favorable for the mixing capsule to be emptied with the minimum possible amount of residues. It can also be advantageous for the emptying of the mixing capsule, particularly in the case of highly viscous material, if the auxiliary chamber has channel-like depressions, for example in the form of grooves. These depressions preferably extend from the bottom of the auxiliary chamber in the direction toward the end face of the auxiliary chamber.
The total volume of the mixing capsule available for mixing is usually in the range of 0.5 to 5 ml, in particular 1 to 3 ml. The volume of the auxiliary chamber is preferably smaller than the volume of the main chamber. The volume of the auxiliary chamber is usually 0.05 ml to 0.5 ml, preferably 0.1 to 0.3 ml.
As appropriate, the maximum diameter of a body deviating from the ball shape, for example in a form with corners and edges, can also be slightly greater than the diameter of the auxiliary chamber. This embodiment is useful in particular when the body is made of a deformable material or comprises such a material. In this case, during activation of the mixing capsule, the body moving relative to the mixing capsule will be deformed by the rapid movement in such a way that it can finally pass as a displacement body into the auxiliary chamber during the dispensing procedure.
Making the body from a deformable material is also expedient to the extent that at the outset, before activation of the mixing capsule, the body can have an edged configuration which during activation initially facilitates the opening of the separating device. During the mixing procedure, the body finally assumes an increasingly rounded configuration which can more readily pass into the auxiliary chamber, but on the other hand leads to much less abrasion of the foil.
It is advantageous if the separating device adheres to an annular surface of the piston, delimiting the auxiliary chamber, and the transition between the annular surface and the inner wall of the auxiliary chamber has a sharp-edged region.
This sharp-edged region preferably runs over a part of the circumference, preferably over substantially 60xc2x0 to 120xc2x0, particularly preferably from 70xc2x0 to 90xc2x0. The transition between annular surface and the inner wall of the auxiliary chamber is preferably rounded in the remaining region. This embodiment prevents the foil from tearing off altogether.
In a particular embodiment, the separating device has a desired breaking point which, independently of the nature of the above-described edge region, contributes to controlled and reliable opening of the auxiliary chamber. The prior damage of the separating device or preparation of a desired breaking point can be effected, for example, by radiation, such as laser radiation, mechanically by scoring or incision using a blade, or thermally by partial fusion or scoring using a heatable blade.
The preparation is preferably carried out only on the plastic part, which may be present, of the separating device, i.e. on the substrate material which is present on one or both sides of a metal layer or SiOx-containing layer. As a result, the seal of the optionally present metal-containing or SiOx-containing layer is maintained.
The preparation can be of any desired shape, but is preferably in a shape which prevents the separating device or parts of this device from tearing off after or during penetration of the separating device by the body.
It has proven expedient for the separating device to be prepared in the form of two or more lines which cross one another in the axis of symmetry of the capsule.
In this case, the separating layer only bursts open at a defined location. This prevents the separating layer or parts of this layer from entering the mixture and impeding the dispensing procedure.
A star-shaped preparation with branching arms can also be used. Such a preparation facilitates the mixing procedure since wedge-shaped foil parts of the separating device in the region of the wall of the auxiliary chamber have a shorter chord length, by which means the component parts of the foil can be more easily turned back during mixing.
Another expedient preparation is one in which a foil part has the outline of a skittle, the head of the skittle being of circular shape and its center point being located on the longitudinal axis of the cartridge. This preparation too facilitates the substantially complete opening of the separating device and thus the access to the auxiliary chamber.
Suitable preparations of the separating device are shown in the figures.
A further advantage of such desired breaking points is that even relatively thick foils, including multilayer foils, in the range from 50 to 80 xcexcm, preferably 60 to 70 xcexcm, can be penetrated with little force (lower mass of the body).
The separating device is preferably in the form of a single-layer or multilayer foil, particularly preferably in the form of a composite foil or a sealing foil. A three-layer foil comprising a plastic outer layer, at least one barrier layer, preferably of plastic, and a sealing layer has proven useful, in which case the sealing layer can also be a plastic foil or a sealing resin.
The foil preferably comprises at least one metal layer, such as an aluminum layer and/or gold layer, and at least one plastic layer, possibly two, three or more plastic layers.
Examples of suitable plastics are: PE, PP, PET, PTFE, PVC, polyamides.
Furthermore, instead of or in addition to the metal foil, the separating device can have plasma-polymerized layers, such as hydrocarbon-containing layers or ceramic barrier layers, such as SiOx layers.
The separating device is attached to the annular end face of the piston, for example by heat-sealing, adhesive bonding, ultrasonic welding or high-frequency welding.
Examples of layers suitable as the outer layer are those comprising PET, PP, PE and/or PA, examples of layers suitable as the barrier layer are those comprising Al and/or SiOx, and examples of layers suitable as the sealing layer are those comprising HDPE, LDPE and/or PP. A coating of PET/Al/LDPE or PA/Al/LDPE has proven expedient.
The layer thicknesses of the individual foils (outer layer, barrier layer, sealing layer) lie in the range of 5 to 60 xcexcm, preferably from 8 to 50 xcexcm.
In order to receive a third component, the separating device can moreover be designed in the form of a foil cushion.
Alternatively, a foil cushion for receiving a third component can be secured on the outer wall of the mixing capsule. It can be secured via a flexible clasp or by gluing. In this embodiment, the outer wall of the mixing capsule is provided with a bore through which the third component can be introduced into the main chamber. The transfer of the third component is preferably effected by applying pressure on the outer foil cushion. The foil cushion, which is arranged on the bore in order to seal the latter, bursts in the area of the bore and empties its content into the main chamber. A comparable embodiment is described in DE 23 24 296 A.
Advantageous materials for the piston of the mixing capsule include metals, such as anodized aluminum, glass, ceramic such as zirconia, plastics and/orxe2x80x94to reduce permeabilityxe2x80x94plastics which are optionally metalized or have undergone vapor deposition or coating with other materials which have a barrier action. Examples of possible plastics include: PE, PP, PET, PTFE, PVC, EVA, polyamides.
Furthermore, combinations of the abovementioned materials, such as a metal insert, preferably made of aluminum, which is surrounded on the outside and on the inside by the plastic, are conceivable. Parts of this type can be produced using the injection-molding process.
The piston can be produced in a two-component injection-molding process. In this process, first of all, by way of example, an inlay is produced, around which, by way of example, PE is then injection-molded.
Nonabrasive materials such as high-density plastics, for example PTFE, inorganic materials with optionally ceramic properties, such as glass, alumina or zirconia, metals such as Fe, Ti, V, Al or stainless steel are suitable for the body of the mixing capsule. The body can be coated with plastic; coatings with PE, PP, PA, PTFE, silicone-containing plastics and/or titanium nitrite have proven expedient.
The components which are contained in the main chamber, the auxiliary chamber and/or, if appropriate, in the separation device, or the foil cushion arranged separately on the outer wall of the mixing capsule, include both liquids and solids, preferably in powder or granule form. However, base substances in paste form are also possible.
In order to avoid damping of the freely movable body by the substances located in the main chamber during the activation procedure, it can also be expedient for these substances to be present in pressed form. The pressed article is preferably located between the end face of the cartridge and the body.
The solids comprise inert fillers, such as finely ground quartz, SiOx-containing substances, glass materials, reactive fillers of all kinds, it being possible for the solids to be surface-modified.
The liquids comprise in particular matrix-forming polymerizable substances, for example polyacids comprising acrylic acid derivatives, methacrylic acid derivatives and maleic acid derivatives, as well as copolymers thereof.
The mixing capsule is preferably suitable for storing, mixing and dispensing glass ionomer cements.
The dispensing spout on the mixing capsule can be fitted eccentrically on the main chamber. It can also be advantageous to form one or more channels which open into the dispensing spout. A design of this type can be expedient for undisturbed emptying of the mixing capsule.
Furthermore, the dispensing spout is preferably of closable design. Possible embodiments are described, for example, in EP-A-0 157 121 A, in which the dispensing spout is pivotably mounted so that it is closed or open depending on the position of the dispensing spout. It is also contemplated to use a spout displacement cap in order to close the dispensing spout.
The mixing capsule has a coding. Suitable codings are, for example, colored identifiers, for example in the form of colored rings, labels, imprints or electronically readable codes (barcodes). It is also contemplated to provide a plurality of codings. The coding can contain information concerning the mixing time, the material, the manufacturer and/or the expiry date.
Coding of the mixing capsule, or of the substances contained therein, using a colored design of the dispensing spout is particularly advantageous if photosensitive substances are intended to be stored in the mixing capsule. To protect these from incident light, it is often necessary for the piston and/or the cartridge to be colored black. If differently colored substances are to be stored in the cartridge, these substances can no longer be identified through the color of the black piston and/or cartridge.
The color identification or coloring is preferably obtained by two-component injection-molding (two-component injection-molding process) of dispensing spout and cartridge. This is linked with a reduction in the number of parts of the capsule and in a reduction in costs in the manufacturing process.
The piston can also have a deformable, damping geometry in order to attenuate the noise which is caused by the body during activation in a suitable mixer unit. This can be achieved, for example, by providing an annular raised portion, possibly tapering to a point, at the end of the piston.
The invention also relates to a method for mixing and dispensing mixtures from mixing capsules, comprising the following steps:
a) provision of a mixing capsule with at least two chambers in which components of the mixture are stored separated from one another by a separating device, comprising a cartridge, a piston arranged displaceably in the cartridge, a dispensing spout, and at least one freely movable body which can penetrate the separating device and can pass as a displacement body into one of the chambers during the dispensing procedure,
b) insertion of the mixing capsule into a mixer unit with a capsule holder,
c) acceleration of the mixing capsule preferably by rapid translational and/or rotary movement, as a result of which the at least two chambers separated by a separating device are opened to form one mixing space,
d) removal of the mixing capsule from the mixer unit,
e) displacement of the piston by using an application device with a piston rod, as a result of which the mixture produced in step c) is applied onto or into a surface, in particular a hard dental tissue or a tooth cavity, via the dispensing spout of the mixing capsule.
A customary application device comprises a holder for insertion of the mixing capsule and a displaceable piston rod which is dimensioned so that it can move the piston of the mixing capsule in the direction of the dispensing opening.